Question on the g-bodies. A 403 can bolt right up to all a 307's stuff in an 80's Cutlass. If one wanted a stealth performance boost to an 84 H/O or so and got a 403 to do it, how far could you go with it while keeping stock appearance? Casting codes excluded, I'm thinking a 403 long block with its native intake and heads that you'd do some work to, stock quadrajet (no computer), stock air cleaner.

I think you could probably get it to breathe well on the intake side, but I imagine the stock exhaust manifolds would be your limiting factor.

 

there are so many wires and hoses on the top of the motor,you could hide any carb and intake on it. or have chris do an aluminum one with 307 numbers

 

Do you want to know how much power you can make with it looking stock on the outside? Are you planning on doing more than what you mentioned in your post? What parts are a must for you to keep? For example, does it have to use the 307 exhaust manifolds/crossover pipe/cat/fake dual exhaust setup or are you open to running true duals?

 

The intake side isn't too bad, the exhaust plain sucks. Get early 330 or 350 heads and reasonable cam and 403 will plain make the 307 look sickly. There was a 40 HP dyno difference between 455 W/Z performance manifolds and headers on W30 build. Olds just assumed people buying their performance cars would immediately put on headers. Pontiac has much better manifolds available in comparison. Just imagine how much worse regular SBO manifolds flow, just a terrible design for a performance build. The cat is also stupid restrictive.

 

DoubleV, basically I'd like it to pass a hood open car show casual glance. I live in a no emissions testing state, and would have no issue running good exhaust. This is just a thinking exercise at the moment, but hypothetically, I'd take a 403, upgrade internals, do some head work and intake work, and make a strong, fun, street engine that would do better on the track than a stock H/O. No real ET number in mind here, other than decisive stomping in a heads up race over a bone stock one.

Olds307403, I can do the early heads on a 403 block. I may want to stay with manifolds, but they don't have to be the stock ones, if there are better flowing ones out there. However, if it's a matter of 50 horses, maybe the headers and just don't open the hood is a better idea. The cat would be more gone than the King of Rock n Roll, don't worry.

OldOlds, good point on the hoses up there. Maybe I could hide a TBI fuel injection setup, lol. If one de-computerizes an H/O, how does one control the lockup converter?

Thanks, all.

 

Easily done.

Don't bother with a TBI setup. Just use a late model Qjet. If you wanted to you could even keep your 403 on the computer.

Lockup can be achieved by one of the various aftermarket kits. I personally run the Painless kit and like it.

 

I would suggest C heads with the proper port-matched intake. Yeah, you have to take some steps to get the right CR, but the flow rate of the BBO ports is a much better match for a 403. Keep in mind that C heads with big valves were used on the 400 BBO.

 

Yeah, the computer can go the way of the birds. The easiest and most straightforward thing would be to just run a normal qjet. Someday I'll fuel inject one for fun. That painless kit seems straightforward enough. When did the lockup engage in regards to fourth gear? Same time?

Joe, that sounds fine. Sitting "BBO" heads on a "SBO" just causes the intake to be sitting too low, correct? And you fix via what you said?

 

No. The BBO and SBO heads are dimensionally identical. When bolted to the SBO block, the intake flanges and bolts will be in exactly the same place as with the SBO heads. That means that the intake is also in exactly the same place. The only difference is that the BBO intake ports have a larger cross section, so you need to port-match the intake side to avoid a mismatch that will cause turbulence and a flow disruption. The Performer RPM is one intake with sufficient meat to allow this port matching.

 

Pretty much locks up a split second after going into 4th gear. I have the proper delay valve ( which is what GM used on their non-CCC cars ) and I didn't really notice much delay. In fact, I'm running 2 delay valves just to see if that makes a difference. Again though, didn't notice any difference. Obviously you don't need a delay valve. They're hard to find too.